9,9-disubstituted,2,7-dibromo fluorenes are useful starting materials for numerous polymers including polymeric light emitting diodes. Bromination at the 2 and 7 position creates sites for polymerization of the fluorene monomer. Dialkylation at the 9 positions advantageously increases solubility for creation of polymer films.
The use of alkali metal hydroxides in the dialkylation of fluorene is reported. However, in most reports polar aprotic solvents are also used. Additionally, only bromoalkanes are used as the alkylating-agent.
Alkylation of fluorene without a polar aprotic solvent in the presence of aqueous (50%) sodium hydroxide and the phase transfer catalyst triethyl benzylammonium chloride at temperatures of 90 to 100 degrees C. is reported in Makosza, Bulletin L'Academie Polonaise Des Sciences, 1967, 15 165-67. However, the reported reaction produced a mixture of 9-butylfluorene and 9,9-dibutylfluroene. The percentage yield is not indicated. Makosza then states that “[b]etter results were obtained when a small amount of dimethylsulphoxide (DMSO) was added.” Id at 166. The result using DMSO yielded a 65% mixture of 9,9 -dibutylfluorene and 9-butylfluorne. Id. at 167.
Additionally, dibromo dialkyl fluorene has been produced through alkylation of 2,7-dibromo fluorene. However, the 9,9-alkylation conducted via that route also required use of a polar aprotic solvent.
Use of a polar aprotic solvent and other solvents present disadvantages relating to waste disposal requirements and disposal costs.
A process to produce high yields of dibromo dialkyl fluorene using alkali metal hydroxide without the use of polar aprotic solvents would be beneficial. Additionally, a method of alkylation which could use a variety of haloalkanes, especially chloralkanes, would also be desirable.